\section{Conclusion}
\label{sec:risk.conclusion}

In conclusion, risk behavior change in conjunction with failure of
prophylactic interventions can have perverse non-monotone effects on
the spread of diseases.  This study has explicitly identified
sidedness as an attribute of risk behavior change that needs to be
taken into account in public policies for vaccinations and antiviral
treatments.  For one-sided risk behavior change, it is imperative to
have sufficiently high levels of coverage, while two-sided situations
require both high coverage as well as programs aimed at reducing risky
behavior.  Our results echo the central premise of Blower-McLean that
the development of efficacious prophylactic treatments and increasing
their coverage need to go hand in hand with behavioral intervention
strategies.  These issues need to be revisited in the context of new
anti-retroviral treatments being considered for HIV
\cite{karim:science10}.
